1. Technical Field
The present invention relates to a multilayered power inductor and a method for preparing the same.
2. Description of the Related Art
As a demand for small, thin, and multi-functional electronic products is increased, a multilayered power inductor also requires large-current components. In order to improve high-current characteristics keeping pace with thinness and multi-functional characteristics, there is a need to reform a material and utilize advantages between respective materials based on complexation of the materials.
In the case of the multilayered power inductor, as a material of a magnetic layer body, ferrite having a quaternary structure such as Ni—Zn—Cu—Fe is used. However, a saturation magnetization value of the material is lower than that of a metallic material, such that it is difficult to implement specifications required for high current characteristics. Therefore, a mixture of the ferrite material and a metal alloy has been mainly used.
As the power inductor becomes smaller and smaller, it is difficult to increase capacity. Therefore, in order to increase capacity, there is a need to increase a volume ratio of a metal alloy that is a magnetic material. To this end, the related art has used a method for mixing a large particle with a small particle at a predetermined ratio with resin to maximally increase a filling ratio. In this case, a volume ratio of the magnetic material may be difficult to implement 85% or more.
As in a sectional structure of FIG. 1, the multilayered power inductor according to the related art is configured to include a magnetic layer body 10 made of a ferrite material having a quaternary structure such as Ni—Zn—Cu—Fe, an inner electrode layer 20, and an outer electrode layer 30. The inner electrode layer 20 and the outer electrode layer 30 mainly use silver (Ag) and the outer electrode layer 30 may further include a plating layer.
Referring to FIG. 2A schematically illustrating an inside of the multilayered power inductor, the magnetic layer body 10 is formed by dispersing a metal powder 11 made of a metal alloy within an insulating resin 12. In this case, the inner electrode layer 20 has mainly used an electrode made of silver (Ag) or copper (Cu).
However, in the case of the metal powder made of the metal alloy forming the magnetic layer 10, a saturation magnetization value is high or a high frequency eddy current loss and a hysteresis loss are increased, such that a material loss may be severe in a high frequency. Therefore, as illustrated in FIG. 2B, in order to reduce the loss of the metal alloy powder 11 having the high eddy current loss, a surface may be coated with glass.
As the insulating resin 12 used for the magnetic layer 10 an epoxy resin is mainly used, which serves to insulate between the metal alloys.
In order to maximally increase capacity of the multilayered power inductor, there is a need to maximally increase the filling ratio of the metal alloy powder (magnetic material) of the magnetic layer implementing magnetic characteristics. To this end, the multilayered power inductor has a structure which a powder having a large grain size is mixed with a powder having a small grain size at an optimal ratio to maximally increase a content of the metal alloy powder and uses an insulating resin as a matrix to support this.
However, even in this case, the metal alloy powders structurally have empty spaces, such that there is a limitation in increasing the filling ratio of the metal alloy powder to 85% or more within the magnetic layer. As a result, it is very difficult to improve the capacity characteristics of the multilayered power inductor.